Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$215.43	4.827%	$225.8288	$225.83	$225.85	$225.80
Purchase #2	$249.39	7.294%	$267.5805	$267.58	$267.60	$267.60
Purchase #3	$41.81	8.125%	$45.2071	$45.21	$45.20	$45.20
Purchase #4	$158.54	8.640%	$172.2379	$172.24	$172.25	$172.20
Purchase #5	$17.98	13.336%	$20.3778	$20.38	$20.40	$20.40
Purchase #6	$44.31	3.116%	$45.6907	$45.69	$45.70	$45.70
Purchase #7	$215.89	3.577%	$223.6124	$223.61	$223.60	$223.60
7 purchase totals =	$943.35		$1,000.5352	$1,000.54	$1,000.60	$1,000.50